[Mailman-Users] help - urgent

[Andrew Barter]

A lot of the mail that the mailman sends out is getting rejected, because the sending email address has a domain which is unknown.

(kojoworld-admin at xxx.xxx.xxx.xxx>: Sender address rejected: Domain not found)

Above the xxx is our IP address.

Any ideas on how to change the sending address so that it used a proper domain?
Any info would be great.

Thankyou.

Andrew.